Title:
Panel-Mounted Aircraft Control Stick
Kind Code:
A1


Abstract:
A panel-mounted control stick for aircraft providing for roll and pitch input that emulates the response of a traditional floor-mounted control stick. The panel-mounted control stick incorporates a pitch beam input assembly and a roll input assembly for translating the movements of the control stick into movements of aircraft control surfaces.



Inventors:
Taylor, Jeremy Phillip (Bel Aire, KS, US)
Application Number:
12/266271
Publication Date:
12/31/2009
Filing Date:
11/06/2008
Assignee:
Cessna Aircraft Company
Primary Class:
International Classes:
B64C13/04
View Patent Images:



Primary Examiner:
DIXON, KEITH L
Attorney, Agent or Firm:
Erise IP, P.A. (Overland Park, KS, US)
Claims:
1. A panel-mounted control stick module for controlling an aircraft comprising; at least one control stick assembly for receiving an input from a user; and a pitch beam assembly, said control stick assembly, upon receiving said input, rotating said pitch beam assembly for the purpose of translating a first control surface of the aircraft.

2. The panel-mounted control stick of claim 1 wherein, the control stick assembly, upon receiving a second input, translates a second control surface of the aircraft.

3. The panel-mounted control stick of claim 2 wherein the at least one control stick assembly comprises: a control stick grip; a control stick shaft; and a roll input assembly; wherein the control stick grip is mounted on a first end of the control stick shaft and is substantially perpendicular to the control stick shaft; wherein the roll input assembly is rotatably attached to the frame of the aircraft; and wherein the control stick shaft is supported by the roll input assembly.

4. The panel-mounted control stick of claim 3 wherein the roll input assembly comprises: a first bellcrank and a second bellcrank, wherein each bellcrank is rotatably attached to the frame of the aircraft at a first end of each bellcrank; a first spool bearing and a second spool bearing; a first spool bearing bolt and a second spool bearing bolt; a shaft retainer; wherein the first spool bearing depends from and is rotatably attached to a second end of the first bellcrank by the first spool bearing bolt; wherein the second spool bearing depends from and is rotatably attached to a second end of the second bellcrank by the second spool bearing bolt; wherein the control stick shaft is maintained between the first spool bearing and the second spool bearing with longitudinal and pivotal freedom of movement; wherein the first spool bearing bolt and the second spool bearing bolt are rotatably maintained adjacent to and in support of the control stick shaft by the shaft retainer; wherein transverse translation of the control stick shaft translates the first and second spool bearing and the first and second bellcrank for the purpose of translating the control surfaces of the aircraft.

5. The panel-mounted control stick of claim 4 wherein the first and second spool bearing each comprise: a top bearing and a bottom bearing; wherein the top bearing and the bottom bearing are frusto-conical in shape and include a cylindrical hole along the conical axis thereof to receive the spool bearing bolt.

6. The panel-mounted control stick of claim 5 wherein the bottom bearings and the top bearings each have a conical surface, a base and a tip; and wherein the bottom bearing and the top bearing depend from the spool bearing bolt with the tip of the top bearing substantially parallel and slightly removed from the tip of the bottom bearing; and wherein the control stick shaft is maintained between the conical surfaces of the top and bottom bearings.

7. The panel-mounted control stick of claim 3, wherein the pitch beam assembly comprises: a pitch beam shaft; a pitch beam input assembly; wherein the pitch beam shaft is rotatably attached to the frame of the aircraft around an axis of rotation; wherein the pitch beam input assembly connects the control stick shaft to the pitch beam shaft; and wherein longitudinal movement of the control stick shaft rotates the pitch beam input assembly and the pitch beam around the axis of rotation.

8. The panel-mounted stick of claim 7, wherein the pitch beam input assembly comprises: a control shaft bracket fixedly attached to a second end of the control shaft; a first pitch beam bracket and second pitch beam bracket, wherein both pitch beam brackets are fixedly attached to the pitch beam at a first end of each pitch beam bracket; a swivel assembly rotatably attached between the second end of the pitch beam brackets wherein the axis of rotation of the swivel assembly with the pitch beam brackets is substantially parallel to the axis of rotation of the pitch beam; and wherein the swivel assembly is rotatably attached to the control stick bracket by a control stick swivel bolt whose longitudinal axis is substantially perpendicular to the longitudinal axis of the pitch beam swivel bolt, and further whose longitudinal axis is substantially perpendicular to the control stick bracket; wherein longitudinal translation of the control stick bracket rotationally translates the pitch beam for the purpose of translating the control surfaces of the aircraft.

9. A control system comprising: an input receiving member for receiving input from a user of the control system; a input translating member for translating the input received by the input receiving member to a first attitudinal control member for controlling the attitude of an aircraft in a first dimension and a first rotational translation member for controlling the attitude of the aircraft in a second dimension; wherein the first rotational translation member is rotatably attached to a multi-directional connecting member for communicating; wherein the multi-directional connecting member is rotatably attached to a second rotational translation member; and wherein the second rotational translation member translates a second attitudinal control member.

10. The control system of claim 9 wherein the input translating member translates the first attitudinal control member in a plane of translation that is substantially perpendicular to the plane of translation of the first rotational translation member.

11. The control system of claim 9 wherein the rotatable attachment of the first rotational translation member to the multi-directional connecting member is substantially perpendicular to rotatable attachment of the multi-directional connecting member to the second rotational translation member.

12. A panel mounted control stick for controlling the attitude of an aircraft comprising: a control stick grip for receiving input from a pilot of the aircraft, containing a socket for receiving a first end of the control stick shaft; said control stick shaft being supported at a point substantially at its midpoint between a first and second spool bearings; said first and second spool bearings depending from and rotatably attached to a first and second bellcrank, respectively; said first and second bellcrank being rotatably attached to the frame of the aircraft and to control surfaces of the aircraft; said control stick shaft being connected at a second end to a control stick bracket; said control stick bracket being rotatably connected to a swivel assembly; said swivel assembly being rotatably connected to a pitch beam bracket; said pitch beam bracket being attached to a pitch beam and to control surfaces of the aircraft; wherein transverse translation of the control stick shaft translates the first and second spool bearings and the first and second bellcranks, for translating the control surfaces of the aircraft; and wherein longitudinal translation of the control stick shaft translates the pitch beam, for translating the control surfaces of the aircraft.

Description:

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent application Ser. No. 12/163,388 filed on Jun. 27, 2008, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to aircraft. More specifically, the invention relates to the field of control systems design.

2. Description of the Related Art

Traditional, floor-mounted control sticks for input of pitch and roll movements to an aircraft have long been known in the aviation arts. Such control sticks have significant drawbacks. These sticks make it difficult for pilots to get into and out of the cockpit because the stick blocks access to the floor of the cockpit, and the pilot must climb over it to get into the pilot's seat. Side-mounted sticks provide easier access than a traditional control stick, but may only be operated with one hand and lack the mechanical advantage of the center mounted stick. An alternative panel-mounted yoke also provides easier access, but may cause safety issues due to a limited range of motion due to obstruction of the yoke by the pilot's legs. The panel-mounted stick disclosed in this application addresses these, and other, issues in aircraft control systems.

SUMMARY

The invention is defined by the claims below. Embodiments of the invention include a panel-mounted control stick for controlling the pitch and roll of an aircraft. The system includes a pitch beam assembly and a control stick assembly. The pitch beam assembly includes a pitch beam and a pitch beam input assembly. The pitch beam assembly, in embodiments, includes a control stick bracket, a pitch beam bracket, and a swivel assembly. The roll input assembly, in embodiments, includes two bellcranks, two spool bearings, and a shaft retainer.

BRIEF DESCRIPTION OF THE DRAWINGS

Illustrative embodiments of the present invention are described in detail below with reference to the attached drawing figures, which are incorporated by reference herein:

FIG. 1 is a perspective view of an aircraft incorporating an embodiment of the panel-mounted control stick;

FIG. 2 is a perspective view of an embodiment of the panel-mounted control stick;

FIG. 3 is a side view of an embodiment of the panel-mounted control stick;

FIG. 4 is a detailed side view of an embodiment of the pitch beam input assembly;

FIG. 5 is a cross-sectional view of an embodiment of the pitch beam input assembly;

FIG. 6 is a top view of an embodiment of the panel-mounted control stick;

FIG. 7 is a conceptual view of a traditional aircraft control stick;

FIG. 8 is an end view of an embodiment of the panel-mounted control stick;

FIG. 9 is detailed top view of an embodiment of the roll input assembly;

FIG. 10 is a cross-sectional view of an embodiment of the roll input assembly.

FIG. 11 is a detailed top view of an embodiment of the roll input assembly; and.

FIG. 12 is a cross-sectional view of an embodiment of the roll input assembly.

DETAILED DESCRIPTION

Referring now to FIG. 1, an aircraft 100 contains an embodiment of control stick module 102 located in the cockpit area of aircraft 100. Aircraft 100 shown in FIG. 1 is a small aircraft commonly known in aviation; however the panel-mounted control stick could be utilized in numerous other sorts of aircraft and other aircraft designs instead of that shown in FIG. 1. Aircraft 100 includes various control surfaces, including an aileron pair 104 for controlling the roll of aircraft 100 and an elevator pair 106 for controlling the pitch of aircraft 100. The specific control surfaces shown on aircraft 100 may also comprise elevons or various other designs for aircraft control surfaces. The specific design for aircraft 100 shown in FIG. 1 does not form any part of the invention but is merely for illustrative purposes.

Control stick module 102 comprises at least one control stick assembly 108 and pitch beam assembly 110, which will be described in further detail below. FIG. 1 displays an embodiment of the invention comprising two control stick assemblies 108. In other embodiments of the invention there may be only one control stick assembly or the control stick assemblies may be located in different relative configurations.

The control stick assemblies 108 are connected through various linkages to the control surfaces of aircraft 100 to allow for movement thereof in a manner known to those skilled in the art. Thus, pitch and roll are able to be controlled by the pilot of aircraft 100 in flight by manipulating stick assemblies 108. A pilot and optional co-pilot input pitch and roll control to the aircraft 100 by various movements of control stick assemblies 108.

The user inputs necessary for operation of control stick module 102 by a pilot are similar to those of traditional aircraft control sticks known in the aviation arts. Pushing forward on the control stick assembly 108 causes the control surfaces to move and pitch the nose of aircraft 100 down, while pulling back on control stick assembly 108 causes the nose of aircraft 100 to pitch up. Similarly, pushing right on control stick assembly 108 moves the control surfaces causing aircraft 100 to roll right, and pushing left on the control stick assembly 108 causes aircraft 100 to roll left.

Referring now to FIG. 2, a detailed perspective view of an embodiment of the control stick assembly 108 and the pitch beam assembly 110 is shown. Pitch beam assembly 110 comprises a pitch beam 200 and one or more pitch beam input assemblies 202. Each pitch beam input assembly 202 translates movement of one control stick assembly 108 into movement of pitch beam 200 and thus to the appropriate control surfaces, such as elevator 106 through various linkages of types commonly known in the aviation arts.

The control stick assembly 108 comprises control stick shaft/input translating member 204, control stick grip/input receiving member 206 and roll input assembly/first attitudinal control member 208. Control stick grip 206 is utilized by the pilot of aircraft 100 for manual input of roll and pitch control movements, and may be formed of metal, plastic or a combination thereof. Control stick grip 206 incorporates a socket for receiving a first end of control stick shaft 204, and is also secured to shaft 204 by bolts, screws or other similar means of attachment. Grip 206, in the FIG. 2 embodiment, is substantially perpendicular to control stick shaft 204, though it may be inclined slightly forward for comfort of the pilot. Control stick shaft 204 is formed from circular metal tube, though solid bar or shafts with other cross-sectional shapes may be utilized. A second end of control shaft 204 is connected to pitch beam 200 by pitch beam input assembly 202.

Pitch beam input assembly 202 comprises a control stick bracket/first rotational translation member 210, a swivel assembly/multi-directional connecting member 212, and pitch beam brackets/second rotational translation member 214. Brackets 210 and 214 may be formed from bent metal plate, or forged, cast or otherwise shaped as shown. Swivel assembly 212, in the disclosed embodiment, is machined or cast from solid metal. The control stick bracket 210 is attached to the second end of control stick shaft 204 by bolts or other appropriate means of attachment including welding. Alternatively, control stick bracket 210 may be formed as an integral part of control stick shaft 204 through machining, welding, casting or other similar means.

Swivel assembly 212 is rotatably attached to control stick bracket 210 by control stick swivel bolt 216. The rotatable connection allows control stick bracket 210 to rotate around the longitudinal axis of bolt 216 thus allowing the side to side movement of control shaft 204 necessary for the roll input.

Swivel assembly 212 is also rotatably attached to a first end of pitch beam brackets 214 by pitch beam swivel bolt 218. The longitudinal axis of pitch beam swivel bolt 218 is substantially parallel to the functional axis of the pitch beam, as described below. The second ends of pitch beam brackets 214 are each attached by means of welding, bolts or other fixed attachment, to pitch beam 200, such that translation of the first end of pitch beam brackets 214 causes pitch beam 200 to rotate about its functional axis.

During operation of the control stick module 102, fore and aft movement of control stick grip 206 is transmitted along control stick shaft 204 to control stick bracket 210 and swivel assembly 212, which translates the first ends of pitch beam brackets 214. The translation of pitch beam bracket 214 causes pitch beam 200 to rotate around its functional axis. The rotation of pitch beam 200 is transmitted to control surfaces, such as elevator 106, by means of control linkages as known in the aviation arts, such as cables, rods, or wires.

The functional axis of pitch beam 200 may be varied according to the means of mounting pitch beam 200, and may be coincident with the longitudinal axis of pitch beam 200 or may be offset by means of an offset mounting. The embodiment shown in FIG. 2 has an offset functional axis due to pitch beam mounting bracket 220. Bracket 220, in the disclosed embodiments, is formed from metal plate cut to the required shape and attached to pitch beam 200 by welding. Pitch beam mounting bracket 220 is rotatably attached to the frame of aircraft 100 providing support for pitch beam assembly 110 as well as allowing pitch beam 200 to rotate around its functional axis. Additional brackets 220 may be provided as necessary to properly support pitch beam 200.

The roll input assembly 208 provides support to control stick shaft 204 and accepts input of roll commands from the pilot of aircraft 100. Roll input assembly 208 comprises two spool bearings 222, two bellcranks 224, two spool bearing mounting bolts 226 and two bellcrank mounting bolts 228. Bellcranks 224, in the disclosed embodiments, are formed from cast or machined metal.

Spool bearings 222 are formed from metal, or some other suitable material, and have a top, a bottom and an interior concave face. The interior face of the spool bearings 222 is concave in some embodiments. The spool bearings 222 have substantially circular cross-sections parallel to the top and bottom faces thereof, which is more clearly shown in FIG. 9 described below. The cross-sections of spool bearings 222 perpendicular to the top and bottom faces thereof vary based on the geometry of the interior concave face. The concave face may have a substantially semi-circular geometry, as shown in the embodiment shown in FIG. 10. The concave face may alternatively comprise two interior planar surfaces disposed at an angle to each other, one extending from the top surface of the spool bearing 222 and the other extending from the bottom surface of spool bearing 222, and intersecting at a point substantially midway between the top and bottom surfaces of spool bearing 222 and between the outer edge of the top and bottom surfaces and the bolts 226. The spool bearing 222 may also comprise multiple pieces, as shown in FIG. 12 below.

Each spool bearing 222 depends from and is rotatably attached to a bellcrank 224 by spool bearing mounting bolt 226, which extends through spool bearing 222 perpendicular to the top and bottom faces of the bearing 222. Each bellcrank 224 is rotatably attached to the frame of aircraft 100 by a bellcrank mounting bolt 228. An additional embodiment of the spool bearings 222 and the roll input assembly is described and discussed below in relation to FIGS. 11 and 12.

Control linkages, as commonly known in the aviation arts, connect the bellcranks 224 to control surfaces, such as ailerons 104, on aircraft 100. As shaft 204 is translated left or right by movement of grip 206, the shaft 204 exerts a force on the left or right spool bearing 222. The force is transmitted from spool bearing 222 to bellcrank 224, causing the bellcranks 224 to rotate around bolt 228. As bellcranks 224 rotate left or right around bolt 228 the control linkages transfer the movement to the control surfaces thus causing aircraft 100 to roll left or right.

Spool bearings 222 are positioned on opposing sides of shaft 204 and the concave faces of spool bearings 222 support shaft 204 and allow it to translate fore and aft as spool bearings 222 rotate around bolts 226.

Referring now to FIG. 3, a side view of an embodiment of the control stick module 102 is shown. In this view it can be seen that the control bracket 210 secures shaft 204 at an angle 300 to the surface of swivel assembly 212.

Control stick grip 206 is pushed fore and aft by the pilot of aircraft 100 to pitch the nose of the aircraft down and up, respectively. When grip 206 is pushed forward to position 302 control stick shaft 204 translates forward thus rotating pitch beam bracket 214 to fore position 304. When grip 206 is pulled back to aft position 306 then shaft 204 translates aft thus rotating pitch beam bracket 214 to aft position 308.

FIG. 4 provides a detailed side view of an embodiment of the pitch beam input assembly 202. As can be seen more clearly here, angle 300 subtends an arc between a first surface 400 of control stick bracket 210, and a central axis 402 of shaft 204. Bolt 216, around which bracket 210 swivels, is substantially perpendicular to the first surface 400. The angle 404, between axis 402 and the axis of bolt 216, is equal to angle 300 minus 90 degrees. The angle 300 may be varied in different embodiments of the panel-mounted stick, and as is discussed in detail below, altering this angle varies the operation of the panel-mounted stick system.

FIG. 5 is a cross-sectional view of an embodiment of swivel assembly 212, pitch beam bracket 214 and control stick bracket 210 along the line I-I on FIG. 4. Bolt 216 rotatably attaches swivel assembly 212 to bracket 210. Bolt 216 is supported within swivel assembly 212 by bearings 500, which are formed from metal or some other suitable material. Metal washer 502, castellated nut 504 and cotter pin 506 secure bracket 210 to swivel assembly 212. Bolt 218, not shown on FIG. 4, similarly attaches bracket 214 to swivel assembly 212.

FIG. 6 is a top view of an embodiment of the control stick module 102 showing the range of motion of the control stick assembly 108 and the pitch beam assembly 110. As the pilot of aircraft 100 moves the grip 206 to the left and right, control shaft 204 presses against spool bearings 222 causing bellcranks 224 to move left to position 600 and right to position 602, respectively. Control linkages, commonly known in the aviation arts, connect bellcranks 224 to control surfaces of aircraft 100 (e.g., ailerons 104 shown in FIG. 1) for causing the aircraft to roll. At any point of movement left and right between position 600 and position 602, the grip 206 may also be moved fore and aft to actuate the pitch beam input assembly 202.

FIG. 7 is a representation of a traditional control stick as seen from the pilot's location in aircraft 100. A traditional control stick 700 extends vertically from the cockpit floor 702, thus as it is moved left or right the end of the control stick 700 follows an arc around the pivot point of the control stick 700. This causes the longitudinal axis of the grip 704 to tilt from side to side as the stick is translated left or right to positions 706 and 708. The angle of tilt is determined by the extent of movement side to side and by the length 710 of the control stick 700.

FIG. 8 is a view of an embodiment of the control stick module 102 from the pilot's location within the cockpit of aircraft 100. The control stick module 102 emulates the traditional aircraft control stick shown in FIG. 7 in several respects, one of which is the tilt of the control grip 206 as it is translated to the left or right by the pilot of aircraft 100. In the neutral position the longitudinal axis 800 of grip 206 extends perpendicular to the floor of the cockpit of aircraft 100. When moved to the left to position 802 or to the right to position 804 the longitudinal axis 800 of grip 206 tilts to the left or right respectively. The grip 206 tilts in the same manner as though it were on a traditional control stick extending to the floor of the cockpit.

The tilting of grip axis 800 is caused by the rotating of shaft 204 and bracket 210 around bolt 216. The angle 300, shown in FIG. 3, causes the first end of shaft 204 to describe an arc 806 when shaft 204 rotates around bolt 216. The grip 206 is attached in a fixed orientation to the first end of shaft 204 and thus remains substantially perpendicular from this perspective, to the tangent of the arc 806 described by shaft 204 which causes the grip to tilt as it is moved from side to side. This movement of grip 206 is equivalent to the movement of grip 206 if attached to the top of a virtual control stick extending to the cockpit floor of aircraft 100. The apparent length of the virtual control stick, x, is:


x=y tan(angle 404) or equivalently x=y tan(angle 300−90 degrees);

where y is the length of control stick shaft 204.

FIG. 9 is a detailed top view of an embodiment of the roll input assembly 208. Bellcrank mounting bolts 228 and spool bearing mounting bolts 226 are secured by castellated nuts 900 and cotter pins 902. Bellcranks 224 have various attachment points for linkages to control surfaces on aircraft 100, such as mounting point 904, mounting bracket 906 and cable guard 908.

FIG. 10 is a cross-sectional view of an embodiment of spool bearings 222 and bellcranks 224 along axis 910 shown in FIG. 9. Spool bearings 222 and bellcranks 224 are secured on bolts 226 by washers 1000 and 1002, and castellated nut 900 and cotter pin 902. In this embodiment of the roll input assembly 208, bolts 226 are disposed with the head of each bold 226 located generally below bellcrank 224 and with castellated nut 900 located generally above bellcrank 224. In addition, the two bolts 226 may be optionally connected by shaft retainer 1004. Retainer 1004 allows bolts 226 to rotate freely in relationship to retainer 1004, but maintains the fixed separation distance between bolts 226 thus securely holds shaft 204 between spool bearings 222. The retainer 1004 and the fixed location of the bellcrank mountings by bolts 228 allow bellcranks 224 to individually rotate about bolts 228 in response to roll input received through shaft 204 while remaining substantially parallel to each other and applying appropriate inputs to control linkages as previously described.

FIG. 11 is a detailed top view of another embodiment of the roll input assembly 208. This embodiment of the roll input assembly includes the same elements described in FIG. 10 above with a different spool bearing design. In this embodiment of the roll input assembly 208 bolts 226 are disposed with the head of each bolt 226 generally located above bellcrank 224, and castellated nuts 900 (see FIG. 12) generally located below bellcrank 224. It additionally includes a retaining clip 1104. Retaining clip 1104 operates in a similar fashion to retainer 1004 to maintain bolts 226 at a fixed distance apart as bellcranks 224 rotate around bolts 228. Retaining clip 1104 is pivotally secured on the top surface of bellcranks 224 and held in place by bolts 226. Alternatively, retaining clip 1104 could be positioned between bellcranks 224 and spool bearings 222.

FIG. 12 is a cross-sectional view of another embodiment of spool bearings 222 and roll input assembly 208 along axis 1106 shown in FIG. 11. Retaining clip 1104 is shown rotatably attached at each end to bolts 226 between a top surface 1201 of each bellcrank 224 and the head of bolt 226 or castellated nut 900, depending on the orientation of bolt 226. Retaining clip 1104 is separated from each bolt 226 by bushing 1202 which extends along bolt 226 a distance slightly more than the width of retaining clip 1104. Washers 1204 separate bushing 1202 from the head of bolt 226 (or alternatively from nut 900) and from top surface 1201 of bellcrank 224. This allows castellated nut 900 to be tightened on bolt 226 without binding clip 1104 and preventing clip 1104 from rotating around bolts 226. One or more washers 1204 may be stacked as necessary, wherever washers 1204 are in use, to adjust for the length of bolt 226, the dimensions of bellcrank 224 and the adjustment of spool bearings 222.

Clip 1004, described in relation to FIG. 10 above, is also separated from bolts 226 by bushing 1206 and washers 1208. This similarly prevents clip 1004 from binding against nut 900 or bolt 226 when tightened. Washers 1208 also separate spool bearings 222 from bellcranks 224 and from nut 900 (or alternatively from the head of bolt 226) to allow for rotation of the spool bearings around bolt 226.

FIG. 12 also shows an alternative embodiment of spool bearings 222 comprising a two part spool bearing 222. In this embodiment of the spool bearings 222, each spool bearing comprises a top bearing 1210 and a bottom bearing 1212. Both top and bottom bearings are frusto-conical in shape, with a cylindrical hole through the axis of the cone to receive bolt 226. The top bearing 1210 has a large circular surface (or base) 1214, a small circular surface (or tip) 1216 and a conical surface 1218. The bottom bearing 1212 has a large circular surface (or base) 1220, a small circular surface (or tip) 1222 and a conical surface 1224. The top bearing 1210 and the bottom bearing 1212 of each spool bearing 222 are positioned relative to each other so that the small surface 1216 of top bearing 1210 is disposed substantially parallel to the small surface 1222 of bottom bearing 1212, and separated therefrom by a short distance. Bolt 226 passes through the cylindrical hole through the conical axis of the top bearing 1210 and bottom bearing 1212, maintaining their linear alignment. Control stick 204 is held against the conical surfaces 1218 and 1224 of the two spool bearings 222 on the two bolts 226, which are maintained the required distance apart by retaining clips 1004 and 1104. The conical surfaces 1218 and 1224 provide support to the control stick 204, while allowing it, through rotation of the spool bearings 222, to move fore and aft to provide input to the pitch beam input assembly. The spool bearings also allow the pilot to control the roll of the aircraft by translating the side-to-side movement of control stick 104 to bellcranks 224 and thus through control linkages, to the control surfaces of the aircraft.

The distance between surfaces 1222 and 1216 is determined by the number of washers 1208, which may be varied to adjust the distance between surfaces 1222 and 1216 to an optimal distance. The optimal distance between the surfaces depends on the circumference of control stick shaft 204 and the optimal friction between shaft 204 and spool bearings 222 when moving the shaft to provide control input to the aircraft.